Easily castable polyurethane propellants containing highly halogenated compounds



United States Patent EASILY CASTABLE PGLYURETHANE PRDPEL- LANTS CONTAKNENG EKG-ELY HALUGENATED COMPOUNDS Raymond L. Cobb and Paul 5. Hudson, Bartlesvilie, Okla, and Lawrence M. Mayiield, Fort Worth, Tern, assignors to Phillips Petroleum Company, a corporation of Delaware No Drawing. Filed Apr. 3, 1958, Ser. No. 726,295

13 Claims. (Ql. 149-419) This invention relates to propellant compositions. In one aspect this invention relates to a method of preparing propellant compositions. In another aspect this invention relates to casting aids for castable propellant compositions.

Special fuels and rocket propellants have achieved considerable military and civil importance. Rocket or jet propulsion motors of the type in which the compositions of this invention can be employed can be used to assist take-0d of a heavily loaded plane or to propel missiles. let propulsion motors of the type which employ the compositions of this invention can also be used in other situations as an auxiliary to a conventional power plant Where an extra surge of power is required. In one of the most convenient types of such jet propulsion or rocket motors, the fuel is located in the combustion chamber itself and is burned with the aid of an oxidizer homogeneously and intimately admixed therewith, thus avoiding the need for complicated feeding arrangements for the fuel and oxidant.

Solid propellants can be prepared by three general methods, -i.e., extrusion, compression molding, and casting of a propellant composition mix. Cast propellants can be prepared by mixing the oxidant component into a curable liquid binder to form a mixture, which mixture is then cast into a mold and cured. In preparing castable propellants it is important that the said mixture possess the proper degree of fluidity in order that it will conform to the mold and the finished propellant will have the desired final configuration.

Various surface active agents such as lecithin, hydrogenated lecithin, dioctyl ester of sodium sulfosuccinic acid (Aerosol OT), sorbitan vmonolaurate, sorbitan monopalmitate, and sorbitan monostearate polyoxyethylene derivatives (Tweens), have been employed as casting aids for castable propellants and While certain improvements have been realized through their use, there is still much to be desired regarding the fluidity of the uncured compositions.

It has now been found that highly halogenated organic compounds when employed in castable propellant compositions markedly improve the fluidity of the mix and render the uncured compositions more adaptable to casting procedures than compositions in which these additives are not present. Thus, broadly speaking, the present invention resides in castable propellant compositions comprising an oxidant component, a curable liquid binder, and a highly halogenated organic compound; and solid propellants prepared from said castable compositions.

An object of this invention is to provide new propellant compositions. Another object of this invention is to provide a method of preparing said new propellant compositions. Still another object of this invention is to provide casting aids for use in castable propellant compositions. Other aspects, objects and advantages of the invention will be apparent to those skilled in the art in view of this disclosure.

Thus according to the invention there is provided a castable propellant composition comprising from 50 to 90 Weight percent of a solid inorganic oxidizing salt as an oxidant component; from 10 to 50 weight percent of a curable liquid binder; and from 0.15 to 5 weight percent of a highly halogenated organic compound.

Any suitable saturated or unsaturated highly halogenated organic compound which is liquid under the conditions of use, i.e., liquid at temperatures of about to about 200 F. which are the temperatures normally employed in mixing the ingredients or" the propellant compositions of the invention, can be usedv as a casting aid in the practice of the invention. Presently preferred casting aids are the highly chlorinated and highly fiuorinated organic compounds, and highly halogenated organic compounds containing both chlorine and fluorine.

One presently preferred group of casting aids are polymers of highly halogenated olefins, said olefins containing :from 2 to 4 carbon atoms per molecule and an average of from 1 to 2 halogen atoms per atom of carbon. The term polymer as used herein and in the claims, unless otherwise specified, is used generically and includes copolymers as Well as homopolymers. Said polymers can be prepared by polymerizing said olefins at temperatures of about 70 to about 200 C. in the presence of peroxide promoters such as benzoyl peroxide and acetyl peroxide. Methods for the preparation of said polymers are well known to those skilled in the art. Further details regarding the preparation of said polymers can be found in Belmore et al., Production of Polyperfiuorovinyl Chloride, Industrial Engineering Chemistry, 39, 338442 (1947) and in US. Patents 2,694,701, issued to Oscar A. Blum et al. on November 16, 1954, 2,784,176, issued to A.L. Dittman on March 5, 1957, and 2,705,706, issued to A. L. Dittman et al. on April 5, 1955.

Examples of said polymers include, among others, the polymers of: trifluorochloroethylene (Kel-F polymer oil); tetrafluoroethylene; perfluorobutadiene; difluorodichloroethylene, including both CF =CCI and OFC1=CFC1;

erfluoropropene; perfluoromonochloropropene; per-fluorobutene; and perfluoromonochlorobutene. Examples of said copolymers are the copolymers of trifiuorochloroethylene with fluorochloroisobutene; tr-ifluorochloroethylone with tetrafiuoroethylene; trifluorochloroethylene with vinylidene fluoride; trifluorochloroethyiene with vinyl fluoride; trifluorochloroethylene with vinyl chloride; trifluorochloroethylene with vinylidene chloride; trifluorochloroethylene with perfluoropropene; and trifiuorochloroethylene with trifiuoroethylene.

The terms perfluoro and perchloro as used herein and in the. claims, unless otherwise specified, define derivatives of carbon and hydrogen containing compounds in which all the hydrogen atoms attached to carbon in the parent compound have been replaced by halogen. For example, perfluorobutene has the formula Another preferred group of casting aids are the highly halogenated organic compounds having from 5 to 30 carbon atoms per molecule, and average halogen content ranging from 0.2 to 2.4 halogen atoms per atom of carbon, and at least 3 halogen atoms per molecule.

Examples of said last group of highly halogenated organic compounds which can be used as casting aids in the practice of the invention include, among others, the

following: highly halogenated hydrocarbons such as Chlorowax-40 (a chlorinated parafiin containing 40 weight percent chlorine), Chlorowax-SO (a chlorinated parafiin containing 50 weight percent chlorine), perfluoromethylcyclohexane, perfluorodimethylcyclohexane, trichlorodecafluoromethylcyclohexane, pentachlorooctafiuoromethylcyclohexane, hexachloroclecafiuorodimethylcyclohexane, octachlorooctafiuorodimethyl-cyclohexane, trichlorotridecafiuorodimethylcyclohexane, perfluoromethylcyclohexene, perfluorodimethylcyclohexene, perfluoroheptene, perfiuorooctene, dichlorodecafiuoroheptene, tetrachlorooctafiuoroheptene, octachlorooctafiuorodecene, trichlorodecafluoroheptene, pentachlorooctafluoroheptane, pentachloropentafluorodecane, decailuoropentadecane, pentadecafluoroeicosane, eicosafiuorotriacontane, perfluoropentane, and pentafluorotrichloropentane, and chlorinated biphenyls containing from to 9 chlorine atoms such as 2,3,4,5,4'-pentachloro-diphenyl; highly hal' ogenated esters such as heptafiuoropropyl acetate, npropyl trifluoroacetate, ethyl perfiuorocaproate, heptafluoropropyl trifluoroacetate, heptafluoropropyl trifiuoropropionate, heptafiuoropropyl pentafiuoropropionate, heptafiuoropropyl trichloroacetate, pentafluoroethyl pentafluoropropionate, and pentafiuorodichloropropyl t rifluoroacetate; highly halogenated tertiary amines such as perchloro-tri-n-butylamine, di (nonafluorobutyl trichloromethylamine, di(nonafiuorobutyl)trifiuoromethylamine, tris(hexafluorot'richlorobutyl)amine, di(undecafiuoropentyl)trichloromethylamine, and di(undecafluoropentyl) pentachloroethylamine; primary and secondary amines in which the amine hydrogen is replaced by fluorine such as N,N-difiuoroundecafluorocyclohexylamine (C F NF N,N-difiuorooctafiuorotrichlorocyclohexylamine 6 a 3 2) N,N-difiuorotridecafiuoromethylcyclohexylamine (CFBCGFIONFZ) N-fiuorodi(nonafiuorobutyl) amine, N,N-difiuorononafluorobutylamine, N fiuorodi(hexafluorotrichlorobutyl) amine, and N-fiuorodi(undecafluoropentyl) amine; and highly halogenated ethers such as perfluoro-di-n-butylether, nonafluorobutyl undecafiuoropentyl ether, trifluoromethyltridecafluorohexyl ether, pentafiuoroethyl tridecafluorohexyl ether, bis(trichlorohexafiuorobutyl) ether, and tri-fluoromethyl tetrachloropentyl ether.

The ChlorowaX-40 and Chlorowax-SO referred to above are products of Diamond Alkali Company. Typical properties of said Chlorowaxes are as follows:

Chloro- Chloro- Wax-40 wax-50 SUS at 100 F., seconds 3, 200 16, 970 Specific gravity, 25 C./25 C 1.15 1.18 Pour point, D C 0 10 Refractive index- 1. 504 l. 518 Gardner color 2 2 prepare the propellant compositions of the invention. Presently preferred polyurethanes are those prepared by the interaction of a polyisocyanate with an active hydrogen-containing compound selected from the group con sisting of aliphatic saturated and unsaturated polyhydroxy compounds and polyamino compounds containing at least one active hydrogen atom.

Said polyurethane monomers are usually reacted in substantially stoichiometric amounts. However, said active hydrogen-containing compound can be used in amounts up to 15 weight percent in excess of stoichiometric and said diisocyanate can be used in amounts up to 25 weight percent in excess of stoichiometric.

While organic polyisocyanates in general can be used in the practice of this invention, the diisocyanatcs are preferred because of their availability and ease of preparation. Said polyisocyanates should be liquid under the conditions of use defined above. Representative polyisocyanates include, among others, the following: benzenel,3-diisocyanate, benzene-1,4-diisocyanate, hexamethylene diisocyanate, toluene-2,4-d-iisocyanate, toluene-2,5- diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenyl-4g,4'-diisocyanate, diphenyl-3,3-dimethyl-4,4-diisocyanate, 2-chloropropane-1,3-diisocyanate, diphenyl-3,3-dimethoXy-4,4'-diiso.cyanate, naphthalene-1,5-diisocyanate, pentamethylenediisocyanate, tetramethylenediisocyanate, octamethylenediisocyanate, dimethylenediisocyanate, propylene-1,2-diisocyanate, benzene-l,2,4-triisocyanate, toluene-2,3-diisocyanate, diphenyl-2,2-diisocyanate, naphthalene-2,7-diisocyanate, naphthalene-l,8diisocyanate, toluenel-2,4,6-t-riisocyanate, benzene-1,3,5-triisocyanate, benzene-1,2,3-triisocyanate, and toluene-2,3,4-triisocyanate.

Active hydrogen-containing compounds which can be used in the practice of the invention include those which have plasticizing properties and which are known to react with polyisocyanates to form polyurethanes. Compounds which are useful for this purpose in the practice of the invention are those which contain hydroxyl and/or amino groups, each of said amino groups containing at least one active hydrogen atom, and which are reactive with an isocyanate group, -NCO. Compounds employed have two or more of said reactive hydrogen-containing groups in the molecule. Commonly, the preferred compounds are glycols and hydroxy containing esters, including polyglycols and polyesters. Polyamino compounds including diamines such as putrescine and cadaver-inc can also be employed. Triols such as glycerol and tetrols such as erythritol can also be used. Natural products which are particularly useful include castor oil, which comprises a glyceride of ricinoleic acid, and recinoleyl alcohol, and mixtures thereof. Said active hydrogen containing compounds should be liquid under the conditions of use defined above.

Other examples of these active hydrogen containing compounds include alkylene glycols such as ethylene glycol, diethylene glycol, tetraethylene glycol, ncopentyl glycol, compounds designated as polyethylene glycol and polypropylene glycol having a molecular weight as high as 10,000 and even higher, propylene glycol, dipropylene glycol, mixed glycols such as the ethylene-propylene glycols, butylene glycol, dibutylene glycol, pentarnethylene glycol, n'cinoleyl alcohol, pentaerythritol [2,2-bis(hydroxymethyl)-l,3-propanediol], esters containing two or more OH groups, and the like. The esters can be made by reaction of dicarboxylic acids with glycols. Acids which can be used in the preparation of these esters include adipic, sebacic, succinic, phthalic and ricinoleic. These acids can be reacted with the above-described glycols to give esters of relatively low (e.g., 200-500) to relatively high (10,000 and even higher) molecular weight. Various methods for the preparation of these esters are known. For example, the acid and glycol can be reacted at an acid to glycol mol ratio of between 0.5 and 2 under conditions to promote elimination of the water produced by the reaction. Still another method involves alternate additions of dicarboxylic acid and of glycol.

Still other examples of the active hydrogen containing compounds are ethanolam-ine, diethanolamine, isopropanoline, diisopropanolamine, ethanolisopropanolamine, dibutanolamine, ethanolbutanolamine, ethylencdiamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, propylenediamine, dipropylenetriamine, hexamethylenediamine, heptamethylenediamine, 2,3-dimethyl- 1,6-diaminohexane, 4,6-diethyl-1,5,8-triaminooctane, 3,9- dimethyl-4,8-diisobutyl-1,6, l l-triaminoundecane, 1,5-diamino-Z-pentene, 1,6 dimethyl-l,7-diamino-4-heptene, and 2,8,7-trimethyl-l,6,10-triamino-3-decene.

The binder contains polyurethanes of the type hereinbefore described and, in addition, there may be present one or more plasticizers, wetting agents, antioxidants and curing catalysts. The finished binder frequently contains various compounding ingredients. Thus, it will be understood that herein and in the claims, unless otherwise specified, the term binder is employed generically and includes various conventional compounding ingredients. The binder content of the total propellant composition will usually range from 10 to 50 percent by weight.

In general, any rubber plasticizer which is compatible with the polyurethanes can be employed in these binder compositions. Materials such as dioctyl sebacate; di(l,4, 7-trioxaundecyl)methane; di-( 3,6-dioxadecyl)formal (TP- 903); and dioctyl phthalate are suitable plasticizers. Materials which provide rubber having good low temperature properties are preferred.

Wetting agents aid in 'defiocculating or dispersing the oxidizer, Aerosol T (dioctyl ester of sodium sulfosuccinic acid), lecithin, and Duomeen C diacetate (the diacetate of trimethylene diamine substituted by a coconut oil product) are among the materials which are applicable.

Antioxidants include Flexamine (physical mixture containing 65 percent of a complex diarylamine-ketone reaction product and 35 percent of N,l"I'-diphenyl-p-phenylenediamine), phenyl-beta-naphthylamine, 2,2-methylenebis(4rmethyl-6-tert-butylphenol), and the like. Rubber antioxidants, in general, can be employed or if desired can be omitted.

While the propellant compositions of the invention will cure at ordinary room temperatures on standing, it is sometimes desirable to use curing catalysts and elevated temperatures so as to alter the curing time and the properties of the finished propellant. Suitable curin catalysts include among others, metal complexes such as Ferrocene (dicyclopentadienyl iron) or 2,4-pentane-dione complexes with cobalt, chromium, nickel or iron. The amount of curing catalyst used will generally range from 0 to 1 weight percent based on the total propellant composition.

The curing temperature will be limited by the oxident employed in some cases but will generally be in the range between 70 and 250 F, preferably between 140 and 200 F.

The curing time must be long enough to give required creep resistance and other mechanical properties in the propellant. The time will generally range from around two or three hours when the higher curing temperatures are employed to about seven days when curing is eifected at lower temperatures.

Oxidants which are applicable in the solid propellant compositions of this invention are those oxygen-containing solids which readily give up oxygen and include, for example, ammonium, alkali metal, and alkaline earth metal salts of nitric, perchloric, and chloric acids, and mixtures thereof. Ammonium nitrate and ammonium perchlorate are the preferred oxidizers for use in the solid propellants of this invention. Other specific oxidizers include sodium nitrate, potassium perchlorate, lithium chlorate, calcium nitrate, barium perchlorate, and strontium chlorate. Mixtures of oxidizers are also applicable. In the preparation of the solid rocket propellant compositions, the oxidizers are ground to a particle size, preferably withv in the range between 2 and 300 microns average particle size. The most preferred particle size is from -220 microns. The amount of solid oxidizer used is usually a major amount of the total propellant composition and is generally in the range between 50 and 90 percent by weight of the total propellant composition. If desired, however, the oxidizer can comprise less than 50 percent 6 by weight of the propellant composition, in some instances.

Burning rate catalysts applicable in the invention in clude ammonium dichromate, and metal ferrocyanides and ferricyanides. Ferric ferrocyanides, such as Prussian, Berlin, Hamburg, Chinese, Paris, and Milori blue, soluble ferric ferrocyanide, such as soluble Berlin or Prussian blue which contains potassium ferric ferrocyanide, and ferric ferrocyanide which has been treated with ammonia, are among the materials which can be used. Ferrous ferricyanide, Turnbulls blue is also applicable. A particularly effective burning rate catalyst is Milori blue which is a pigment similar to Prussian blue but having a red tint and is prepared by the oxidation of a paste of potassium ferrocyanide and ferrous sulfate. Other metal compounds such as nickel and copper ferrocyanides can also be employed. The amount of burning rate catalyst used, in the propellant compositions of this invention, is usually in the range of 0 to 16 weight percent based. on the total propellant composition.

High energy additives such as finely divided aluminum, magnesium, boron and other finely divided metals can also be used in the propellant compositions of the invention. Said finely divided metals will usually have a particle size within the range of 1 to 50 microns and will usually be used in amounts within the range of 0 to 20 wei ht percent based on the total propellant composition.

It is to be understood that each of the various types of compoun ing ingredients can be used singly, or mixtures of various ingredients performing a certain function can be employed. It is sometimes preferred, for example, to use mixtures of plasticizers rather than a single material.

The binder forms a continuous phase in the propellant with the oxidant as the discontinuous phase. One procedure for blending the propellant ingredients utilizes a stepwise addition of oxidant and other dry ingredients to the binder mixture. The binder ingredients are mixed to form a binder mixture, and the oxidizer ingredient is then added to said binder mixture in equal subsequent additions, usually four or more.

One presently preferred and convenient method of preparing the castable propellant compositions of the invention comprises blending a solid inorganic oxidizing salt with a highly halogenated organic compound so as to coat said salt with said halogenated compound and form a first mixture. Said first mixture is then blended with an active hydrogen-containing compound to form a a second mixture which is then blended with a polyisocyanate in an amount sui'licient to interact with said active hydrogencontaining compound and form a polyurethane. Other variations in the mixing procedure can be introduced. In some instances all of the ingredients except the polyisocyanate can be blended in one operation and the polyisocyanateis then added. It is even possible with some polyisocyanates to incorporate them with the rest of the ingredients rather than waiting until all of the other ingredients are thoroughly blended.

A general formulation for a propellant composition prepared in accordance with the invention is as follows:

Weight percent Binder 10-50 Polyurethane 10-50 Plasticizer 0-15 Antioxidant 0-5 Surface active agent O-5 Curing catalyst 0-1 Highly halogenated organic compound 0.15-5 Oxidizer 50-90 Burning rate catalyst O-lO Finely divided metal 0-20 The following examples will serve to further illustrate the invention.

Example 1 Two castable propellant compositions containing the following ingredients were prepared.

Propellant Number 1, Wt. 2, Wt. percent percent Castor oil 7. 3 7. 7 Glycerol-propylene oxide condensation product 4. 8 5. 1 Toluene-2,4-diisocyanate 4. 1 4. 3 Dioctyl sebacate 1. 8 1. 9 Lecithin 1 l Kel-F polymer 1 Aluminum powder product) 5 Annnonlum perchlorate, 70/30 3 75 75 1 One mol of glycerol condensed with 9 mols of propylene oxide.

2 Poly-trifiuorochlorocthyleno.

3 Ratio denotes relative amounts of diiicrent particle size material as ih parts, 210 microns.

30 parts, 14-18 microns.

The ammonium perchlorate and Kel-F polymer oil were mixed minutes in a Baker-Perkins mixer. All other ingredients except the diisocyanate were then added. Mixing was continued for 30 minutes at atmospheric pressure and then under vacuum for minutes. Toluene-2,4-diisocyanate was then added and mixing was continued under vacuum for 7 minutes. The material was poured into a mold. It flowed readily under its own weight. For the second composition, all the ingredients except the diisocyanate were mixed 30 minutes in a Baker- Perkins mixer at atmospheric pressure and mixing was then continued under vacuum for 15 minutes. The diisocyanate was then added and mixing was again done under vacuum for 5 minutes. The composition was transferred to a mold. It would flow only when subjected to vibration.

Example II A castable propellant composition contained the following ingredients:

1 As in Example I.

2 Di(1,4,7-trioxaundecyl)methane. The product as prepared (TP-DOB) topped to remove low boiling materials is designated as ZP-2l1.

The ammonium perchlorate and Kel-F polymer oil were mixed for 15 minutes in a Baker-Perkins mixer. The rest of the ingredients were added and mixing was effected under vacuum for 45 minutes. The material was transferred to a mold. It flowed when subjected to vibration. The molded specimen was cured 48 hours at 160 F. Small strips or strands approximately x 6 were cut from the molded specimen and burning rate tests were run in a standard strand burning bomb. Results were as follows:

r at 600 p.s.i., in./sec 0.245 r at 1000 p.s.i., in./sec 0.305 n 250560 p.s.i 0.12 560-880 p.s.i 0.57 880150O p.s.i 0.02

Pressure exponent in r=aP" Where a is a constant, Peis average chamber pressure, and r is burning rate.

When a similar composition to that described above is prepared without KelP polymer oil, it flows with great difiiculty even when vibrated.

Example III The following ingredients were employed in preparing a castable propellant composition:

1 2-l1ydroxyet'ny1 ricinoleate.

A chlorinated par-afiiu containing chlorine.

Ratio denotes relative amounts of different particle size mzrterinl as follows:

no parts, 210 microns. 24 parts, 1'418 microns.

All ingredients except the toluene-2,4-diisocyanate were mixed at atmospheric pressure in a Baker-Perkins mixer for 45 minutes, the diisocyanate was then added and mixing was continued under vacuum for 10 minutes. The composition was then poured into a mold. It flowed easily under its own weight. It was cured 48 hours at 160 F. Tensile specimens were cut from the cured sample. These speciments were A inch thick with the test section being inch wide and 2 inches long. The test section was joined by /2 inch radii to 1 inch x 1 inch tabs at either end. The samples, being stored, were equilibrated at 70 F. and tensile tests made using a cross-head speed of 2 inches per minute. The etfective gage length of the spech'nen was 2.6 inches. Results are as follows:

40 weight percent Modulus of elasticity, p.s.i 8710 Maximum stress, p.s.i 354 Elongation at maximum stress, percent 6.7 Ultimate stress, p.s.i 338 Ultimate elongation, percent 8.0

Example IV The following ingredients were employed in preparing a castable propellant composition:

As in Example III.

The mixing procedure described in Example III was employed. The composition flowed under its own weight. It was poured into a mold, cured, and tensile specimens were cut from the molded slab in the manner described in Example III. Results of tests were as follows:

Modulus of elasticity, p.s.i 5010 Maximum stress, p.s.i 315 Elongation at maximum stress, percent 11.5 Ultimate stress, p.s.i 264 Ultimate elongation, percent 16.6

The above examples clearly demonstrate the effectiveness of the casting aids of the invention.

As will be evident to those skilled in the art various other modifications of the invention can be made, or followed, in view of the above disclosure, without departing from the spirit or scope of the invention.

We claim:

1. A solid propellant composition comprising a mixture of: from 50 to weight percent of a solid inorganic oxidizing salt as an oxidant component; from 10 to 50 weight percent of a binder component comprising a polyurethane; and from 0.15 to 5 weight percent of a highly halogenated organic compound which is liquid at temperatures employed in mixing said composition and which is selected from the group consisting of (1) highly halogenated organic compounds having from to 30 carbon atoms per molecule, an average halogen content ranging from 0.2 to 2.4 halogen atoms per atom of carbon, and at least 3 halogen atoms per molecule, and (2) polymers of highly halogenated olefins, said olefins'containing from' 2 to 4 carbon atoms per molecule and an average of from 1 to 2 halogen atoms per atom of carbon; all of said halogen atoms being selected from the group consisting of chlorine and fluorine.

2. A castable propellant composition comprising a mixture of: from 50 to 90 weight percent of a solid inorganic oxidizing salt as an oxidant component; from to 50 weight percent of a curable liquid binder comprising an active hydrogen containing compound selected from the group consisting of polyhydroxy compounds and polyamino compounds containing at least one active hydrogen atom, and a polyisocyanate capable of reacting with each other to form a polyurethane, said active hydrogen containing compound and said polyisocyanate being present in amounts ranging from substantially stoichiometric to about weight percent excess for the active hydrogen containing compound and from substantially stoichiometric to about 25 weight percent excess for the polyisocyanate; and from 0.15 to 5 weight percent of a highly halogenated organic compound which is liquid at temperatures employed in mixing said composition and which is selected from the group consisting of (1) highly halogenated organic compounds having from 5 to 30 carbon atoms per molecule, an average halogen content ranging from 0.2 to 2.4 halogen atoms per atom of carbon, and at least 3 halogen atoms per molecule, and (2) polymers of highly halogenated olefins, said olefins containing from 2 to 4 carbon atoms per molecule and an average of from 1 to 2 halogen atoms per atom of carbon; all of said halogen atoms being selected from the group consisting of chlorine and fluorine.

3. A solid propellant composition comprising a mixture of: from 50 to 90 weight percent of a solid inorganic oxidizing salt as an oxidant component; from 10 to 50 weight percent of a binder component comprising a polyurethane formed by the interaction of a polyisocyanate and an active hydrogen containing compound selected from the group consisting of polyhydroxy compounds and polyamino compounds containing at least one active hydrogen atom; and from 0.15 to 5 weight percent of a highly halogenated organic compound which is liquid at temperatures employed in mixing said composition and which is selected from the group consisting of (1) highly halo genated organic compounds having from 5 to 30 carbon atoms per molecule, an average halogen content ranging from 0.2 to 2.4 halogen atoms per atom of carbon, and at least 3 halogen atoms per molecule, and (2) polymers of highly halogenated olefins, said olefins containing from 2 to 4 carbon atoms per molecule and an average of from 1 to 2 halogen atoms per atom of carbon; all of said halogen atoms being selected from the group consisting of chlorine and fluorine.

4. A propellant composition according to claim 3 wherein said active hydrogen containing compound is castor oil.

5. A propellant composition according to claim 3 wherein said polyisocyanate is toluene-2,4-diisocyanate.

10 6. A propellant composition according to claim 3 wherein said highly halogenated organic compound is polytriiluorochloroethylene.

7. A propellant composition according to claim 3 wherein said highly halogenated organic compound is a chlorinated paraflin hydrocarbon containing about 40 to about 50 weight percent of chlorine.

8. A propellant composition according to claim 3 wherein said highly halogenated organic compound is heptafiuoropropyl acetate.

9. A propellant composition according to claim 3 wherein said highly halogenated organic compound is perfluorodimethylcyclohexane.

10. A propellant composition according to claim 3 wherein said highly halogenated organic compound is perfluorodi-n-butyl ether.

11. A propellant composition according to claim 3 wherein said highly halogenated organic compound is 2,3,4,5,4-pentachloro-diphenyl.

12. A propellant composition according to claim 2 wherein said oxidant component is ammonium perchlorate; said polyurethane is formed by the interaction of castor oil and toluene-2,4-diisocyanate; and said highly halogenated organic compound is polytrifluorochloro' ethylene. 1 l

13. A solid propellant composition comprising a mixture of: from 50 to 90 weight percent ofv a solid inorganic oxidizing salt as an oxidant component; from 10 to 50 weight percent of a binder component comprising a polyurethane; and from 0.15 to 5 Weight percent of a highly halogenated organic compound which is liquid at temperatures employed in mixing said composition and which is selected from the group consisting of 1) compounds having from 5 to 30 carbon atoms per molecule, an average halogen content ranging from 0.2 to 2.4 halogen atoms per atom of carbon, at least three halogen atoms per molecule, and being selected from the group consisting of saturated and unsaturated hydrocarbons, esters, and tertiary amines, and (2) polymers of highly halogenated olefins, said olefins containing from 2 to 4 carbon atoms per molecule and an average of from 1 to 2 halogen atoms per atom of carbon; all of said halogen atoms being selected from the group consisting of chlorine and fluorine.

References Cited in the file of this patent UNITED STATES PATENTS 2,857,258 Thomas 'Oct. 21, 1958 FOREIGN PATENTS 655,585 Great Britain July 25, 1951 OTHER REFERENCES Modern Plastics Encyclopedia, Plastics Catalogue Corp., 575 Madison Ave., N.Y. 22, N.Y. (1953), page 99.

Zaehringer: Chem. Engineering Progress, vol. 51, No. 7, July 1955, page 302.

Blatz: Ind. and Eng. Chem., vol. 48, No. 4, April 1956, pp. 727-9.

Arendal: Ind. and Eng. Chem, vol. 48, No. 4, April 1956, pp. 725-6.

Zaehringer: Modern Plastics, vol. 34, October 1956, pp. 148-51, 284 (note p. 149). 

1. A SOLID PROPELLANT COMPOSITION COMPRISING A MIXTURE OF: FROM 50 TO 90 WEIGHT PERCENT OF A SOLID INORGANIC OXIDIZING SALT AS AN OXIDANT COMPONENT; FROM 10 TO 50 WEIGHT PERCENT OF A BINDER COMPONENT COMPRISING A POLYURETHANE; AND FROM 0.15 TO 5 WEIGHT PERCENT OF A HIGHLY HALOGENATED ORGANIC COMPOUND WHICH IS LIQUID AT TEMPERATURES EMPLOYED IN MIXING SAID COMPOSITION AND WHICH IS SELECTED FROM THE GROUP CONSISTING OF (1) HIGHLY HALOGENATED ORGANIC COMPOUNDS HAVING FROM 5 TO 30 CARBON ATOMS PER MOLECULE, AN AVERAGE HALOGEN CONTENT RANGING FROM 0.2 TO 2.4 HALOGEN ATOMS PER ATOM OF CARBON, AND AT LEAST 3 HALOGEN ATOMS PER MOLECULE, AND (2) POLYMERS OF HIGHLY HALOGENATED OLEFINS, SAID OLEFINS CONTAINING FROM 1 TO 2 HALOGEN ATOMS PER ATOM OF CARBON; ALL OF SAID HALOGEN ATOMS BEING SELECTED FROM THE GROUP CONSISTING OF CHLORINE AND FLUORINE. 